lots of stabilization of CONFIG_PREEMPT_REALTIME. It's still inexperimental status but general stability is improving.

Changes since -T7:

- fixed a nasty category of bugs that were introduced by the use of rwsems for rwlocks. rwsems are not read-recursive, while rwlocks are. Fortunately it was not too hard to identify & fix recursive users of tasklist_lock, in fact each of these also qualifies as a cleanup. The symptom of this bug was a soft-deadlocking of the system.

- fixed profiler locks, i believe this could resolve the bootup crash reported by K.R. Foley.